feat: rename Docker Watcher to Tinyforge

Rebrand the project as Tinyforge to reflect its evolution from a Docker
container watcher into a self-hosted mini CI/deployment platform.

Rename covers: Go module path, Docker labels, DB/config filenames,
JWT issuer, Dockerfile binary, docker-compose, CI workflows, frontend
i18n, README with static sites docs, and all code comments.

Makefile

@@ -9,7 +9,7 @@ build-frontend:
 
 # Build the Go binary (embeds web/build/ via go:embed).
 build-backend:
-	go build -o docker-watcher ./cmd/server
+	go build -o tinyforge ./cmd/server
 
 # Run in development mode with hot reload.
 # Requires air (go install github.com/air-verse/air@latest).
@@ -18,4 +18,4 @@ dev:
 
 # Clean build artifacts.
 clean:
-	rm -rf web/build web/node_modules/.vite docker-watcher
+	rm -rf web/build web/node_modules/.vite tinyforge